Why no support for HSR for freight trains?

Given all of the interest by the general public and some governments in high-speed rail for passenger trains, why don't Class I freight railroads team up with prospective builders of HSR lines and work things so that HSR lines could be used both for passenger and fast freight trains?

Surely HSR for freight could create a completely new market for high-priority goods, outdo trucks and even compete with air freight.

If a HSR corridor is built, as long as train speeds are the same, surely the corridor would have some capacity for freight.

Has this issue been studied and rejected, or just not given much attention?

Thanks.

The Rate of Return on Investment would be negative for the freight railroads, so they have no interest. FedEx and UPS have shown some interest in HSR for freight in Europe where the Government has already built the High-speed lines, but that is it.
In the US the freight railroads barely have enough money to keep up with the demands for capacity increases for ordinary lines which offer a positive rate of return.

Piling onto JayBee's response, it's more important for Class 1s to have freight reliably get to where it's supposed to be, at the right time, rather than for it to get there faster but not be able to guarantee the arrival time. That, and because of the laws of physics, a train would have to expend a lot of energy to move freight so quickly - at that point, there's not enough differential between ground and air freight for railroads to make a profit.